CN113250056A

CN113250056A - Milling machine with hydraulic damping system

Info

Publication number: CN113250056A
Application number: CN202110113841.3A
Authority: CN
Inventors: E·S·恩格尔曼; C·K·小里夫; M·J·西罗瓦特卡
Original assignee: Caterpillar Paving Products Inc
Current assignee: Caterpillar Paving Products Inc
Priority date: 2020-01-28
Filing date: 2021-01-27
Publication date: 2021-08-13
Also published as: US11015305B1; DE102021101405A1

Abstract

The invention discloses a milling machine. The milling machine may have a frame, first and second tracks connected to a first end of the frame, a third track connected to a second end of the frame, and a milling drum attached to the frame. The milling machine may have first, second, and third actuators connecting the frame and the first, second, and third tracks, respectively. Each actuator may adjust a height of the frame relative to a respective one of the first, second, and third tracks. The milling machine may include a damper assembly attached to each of the first and second actuators. The damper assembly may have an accumulator connected to a respective one of the first and second actuators, and a control valve for controlling fluid flow between the accumulator and the respective one of the first and second actuators.

Description

Milling machine with hydraulic damping system

Technical Field

The present disclosure relates generally to a milling machine, and more particularly to a milling machine having a hydraulic damping system.

Background

The road surface typically includes the uppermost layer of asphalt or concrete on which the vehicle is traveling. Over time, the road surface may wear or may be damaged, for example by cratering or cracking and rutting. The damaged road surface may in turn cause damage to vehicles travelling on the road surface. Damaged road surfaces may be locally repaired by filling in potholes, cracks, and/or ruts. However, it is often desirable to replace worn or damaged road surfaces with new ones. This is usually done by removing a layer of asphalt or concrete from the road and re-paving the road by laying a new layer of asphalt or concrete.

Milling machines are commonly used to remove layers of asphalt or concrete from the surface of roads. A typical milling machine includes a frame supported on wheels or tracks and including a milling drum attached to the frame. As the milling machine travels over the existing road surface, the teeth or cutting tools on the rotating milling drum contact the road surface and tear the road layer. The milling drum chamber typically surrounds the milling drum to contain the milled material. Milled material is typically transported to an adjacent vehicle using a conveyor system, which removes the material from the work site. After the milling process, a new layer of asphalt or concrete may be applied on the milled road surface to create a new road surface.

In another application, it is sometimes desirable to stabilize or rebuild the upper layers of a road or work site. This is typically accomplished by removing the upper layer, mixing it with a stabilizing component such as cement, ash, lime, etc., and depositing the mixture back on top of the road or work site. Milling machines such as stabilizers or earth-filling machines are commonly used for this purpose. Such milling machines also include a frame supported by tracks or wheels, and include a milling drum attached to the frame. The milling drum is enclosed in a drum. The cutting tools or teeth on the milling drum tear the ground and push the removed material towards the rear of the drum. The stabilizing ingredient and/or water is mixed with the milled material, which is then deposited back onto the ground towards the rear of the drum.

In both types of milling machines discussed above, the frame is typically located several feet above the ground. An operator typically controls operation of the milling machine from an operator platform mounted on the frame. When a milling machine is transported on or between work sites, one or more of its tracks or wheels may encounter irregularities (e.g., depressions and/or obstacles on the ground) on the ground surface, which may cause one or more sides of the milling machine frame to suddenly rise or fall. Such sudden height changes may cause discomfort to the operator because the operator is located several feet above the ground surface. Accordingly, it is desirable to create a smoother ride and minimize discomfort for the milling machine operator when transporting the milling machine on or between work sites.

The milling machine and/or hydraulic damping system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.

Disclosure of Invention

In one aspect, the present disclosure is directed to a milling machine. The milling machine may include a frame. The milling machine may also include a first track and a second track connected to the first end of the frame. Additionally, the milling machine may include a third track connected to a second end of the frame disposed opposite the first end. The milling machine may include a first actuator connecting the frame and the first track, a second actuator connecting the frame and the second track, and a third actuator connecting the frame and the third track. Each of the first, second, and third actuators may be configured to adjust a height of the frame relative to a respective one of the first, second, and third tracks. The milling machine may also include a milling drum attached to the frame between the first end and the second end. The milling machine may include a damper assembly attached to at least one of the first actuator and the second actuator. The damper assembly may include an accumulator in fluid communication with at least one of the first and second actuators. The damper assembly may include a control valve configured to control fluid flow between the accumulator and at least one of the first actuator and the second actuator.

In another aspect, the present disclosure is directed to a method of controlling a milling machine. The milling machine may have a frame supported by a pair of front tracks connected to the frame by a pair of front actuators, and by at least one rear track connected to the frame by at least one rear actuator. The milling machine may have a milling drum attached to the frame, and an accumulator connected to at least one of the front actuators. The method may include operating the milling machine, wherein the milling drum is not in contact with the ground surface. The method may further include determining that hydraulic damping has begun. The method may further include selectively controlling a flow of hydraulic fluid from at least one of the front actuators to the accumulator.

In yet another aspect, the present disclosure is directed to a milling machine. The milling machine may include a frame. The milling machine may also include a left front track disposed adjacent the front end of the frame, a right front track disposed adjacent the front end and spaced apart from the left front track, and at least one rear track disposed adjacent the rear end of the frame. Additionally, the milling machine may include a left front actuator connecting the frame and the left front track, a right front actuator connecting the frame and the right front track, and a rear actuator connecting the frame and the at least one rear track. Each of the front left actuator, the front right actuator, and the rear actuator may be configured to selectively adjust a height of the frame relative to the front left track, the front right track, and the at least one rear track, respectively. Each of the front left, front right, and rear actuators may include a front end chamber and a rod end chamber separated by a piston. The milling machine may include a milling drum attached to the frame between the front end and the rear end of the frame. The milling machine may also include an engine configured to propel the left front track, the right front track, and the at least one rear track in a forward or rearward direction and rotate the milling drum. Additionally, the milling machine may include a left damper assembly. The left damper assembly may include a left accumulator. The left damper assembly may also include a left fluid conduit connecting the left accumulator to the front end chamber of the left front actuator. Further, the left damper assembly may include a left control valve disposed in the left fluid conduit. The milling machine may also include a right damper assembly. The right damper assembly may include a right accumulator. The right damper assembly may also include a right fluid conduit connecting the right accumulator to the front end chamber of the right front actuator. Additionally, the right damper assembly may include a right control valve disposed in the right fluid conduit. The milling machine may also include a controller configured to selectively adjust at least one of the left and right control valves.

Drawings

Fig. 1 is an illustration of an exemplary milling machine;

fig. 2 is an illustration of another exemplary milling machine;

fig. 3 is a partial cross-sectional view of an exemplary leg stud of the milling machine of fig. 1 and 2;

fig. 4A is a schematic illustration of an exemplary hydraulic damping system of the milling machine of fig. 1 and 2;

fig. 4B is a schematic illustration of another exemplary hydraulic damping system of the milling machine of fig. 1 and 2;

FIG. 5A is a cross-sectional view of an exemplary accumulator for the hydraulic damping system of FIGS. 4A and 4B;

FIG. 5B is a cross-sectional view of another exemplary accumulator for use with the hydraulic damping system of FIGS. 4A and 4B; and

fig. 6 is an exemplary method of operating the machine of fig. 1 and 2.

Detailed Description

Fig. 1 and 2 illustrate

exemplary milling machines

10 and 20, respectively. In one exemplary embodiment as shown in fig. 1, the milling machine 10 may be a cold planer, which may also be referred to as a cold planer, ripper, model planer, or the like. Milling machine 10 may include a frame 22 that may extend from a first end 24 to a second end 26 disposed opposite first end 24. In some exemplary embodiments, the first end 24 may be a front end and the second end 26 may be a rear end of the frame 22. The frame 22 may have any shape (e.g., rectangular, triangular, square, etc.).

The frame 22 may be supported on one or more propulsion devices. For example, as shown in fig. 1, the frame 22 may be supported on

pushers

28, 30, 32, 34.

Propulsion devices

28, 30, 32, 34 may be equipped with electric or hydraulic motors that may impart motion to

propulsion devices

28, 30, 32, 34 to assist in propelling machine 10 in a forward or rearward direction. In one exemplary embodiment shown in fig. 1, the propelling

devices

28, 30, 32, 34 may take the form of tracks, which may include, for example, sprockets, idlers, and/or one or more rollers that may support a continuous track. However, it is contemplated that the

propulsion devices

28, 30, 32, 34 of the milling machine 10 may take the form of wheels (see fig. 2). In this disclosure, the terms track and wheel will be used interchangeably and will include the other of the two terms.

Tracks

28, 30 may be positioned adjacent first end 24 of frame 22, and tracks 32, 34 may be positioned adjacent second end 26 of frame 22. The tracks 28 may be spaced apart from the tracks 30 along the width of the frame 22. Likewise, tracks 32 may be spaced apart from tracks 34 along the width of frame 22. In one exemplary embodiment shown in FIG. 1, track 28 may be a front left track, track 30 may be a front right track, track 32 may be a rear left track, and track 34 may be a rear right track. Some or all of

propulsion devices

28, 30, 32, 34 may also be steerable, allowing machine 10 to turn right or left during forward or backward movement on ground surface 64. Although the milling machine 10 in fig. 1 has been shown as including four

tracks

28, 30, 32, 34, it is contemplated that in some exemplary embodiments, the milling machine 10 may have only one

rear track

32 or 34, which may be generally centrally located along the width of the frame 22.

The frame 22 may be connected to the

tracks

28, 30, 32, 34 by one or more leg posts 36, 38, 40, 42. For example, as shown in FIG. 1, the frame 22 may be connected to the left front track 28 via a leg strut 36 and to the right front track 30 via a leg strut 38. Likewise, the frame 22 may be connected to the left rear track 32 via a leg strut 40 and to the right rear track 34 by a leg strut 42. One or more of the leg posts 36, 38, 40, 42 may be height adjustable such that the height of the frame 22 relative to one or more of the

tracks

28, 30, 32, 34 may be increased or decreased by adjusting the length of one or more of the leg posts 36, 38, 40, 42, respectively. It should be appreciated that adjusting the height of frame 22 relative to one or more of

tracks

28, 30, 32, 34 will also adjust the height of frame 22 relative to a ground surface 64 on which tracks 28, 30, 32, 34 may be supported.

Milling machine 10 may include a milling drum 50, which may be attached to frame 22 between front end 24 and rear end 26. Milling drum 50 may include cutting tools 52 (or teeth 52) that may be configured to cut and tear a predetermined thickness of the roadway or ground. The height of milling drum 50 relative to ground surface 64 may be adjusted by adjusting the height of one or more of the leg posts 36, 38, 40, 42. As milling drum 50 rotates, teeth 52 of milling drum 50 may come into contact with the ground or road surface, thereby tearing or cutting the ground or road surface. Milling drum 50 may be enclosed within a drum 54, which may help to contain material removed from the ground or road surface by teeth 52. Machine 10 may include one or

more conveyors

56, 58, which may facilitate transporting material removed by milling drum 50 to an adjacent vehicle, such as a dump truck.

Milling machine 10 may include an engine 60 attachable to frame 22. The engine 60 may be any suitable type of internal combustion engine, such as a gasoline, diesel, natural gas, or hybrid engine. However, it is contemplated that in some exemplary embodiments, the engine 60 may be electrically powered. The engine 60 may be configured to deliver rotational power output to one or more hydraulic motors associated with the

propulsion devices

28, 30, 32, 34, to the milling drum 50, and to one or

more transmitters

56, 58. The engine 60 may also be configured to deliver electrical power to operate one or more other components or accessory devices (e.g., pumps, fans, motors, generators, belt drives, transmissions, etc.) associated with the milling machine 10.

Milling machine 10 may include an operator platform 62 attachable to frame 22. In some exemplary embodiments, the operator platform 62 may be in the form of a weather platform, which may or may not include a canopy. In other exemplary embodiments, the operator platform 62 may be in the form of a partially or fully enclosed nacelle. As shown in fig. 1, the operator platform 62 may be located at a height "H" above the ground surface 64. In some exemplary embodiments, the height H may be in a range between about 2 feet and 10 feet above the ground surface 64. Operator platform 62 may include one or more controls 66 that may be used by an operator to operate and/or control milling machine 10. The controller 66 may include one or more input devices 66, which may take the form of buttons, switches, sliders, joysticks, scroll wheels, touch screens, or other input/output or interface devices. Machine 10 may also include a controller 70 that may be configured to receive inputs, data, and/or signals from one or more input devices 66, sensors 72, and/or other sensors associated with milling machine 10, and to control operation of one or more components (e.g., engine 60, milling drum 50,

propulsion devices

28, 30, 32, 34,

transmitters

56, 58, etc.). The controller 70 may include or be associated with one or more processors, memory devices, and/or communication devices. Controller 70 may embody a single microprocessor or multiple microprocessors, Digital Signal Processors (DSPs), application specific integrated circuit devices (ASICs), and the like. Many commercially available microprocessors can be configured to perform the functions of controller 70. Various other known circuits may be associated with controller 70, including power supply circuitry, signal conditioning circuitry, and communication circuitry.

One or more memory devices associated with the controller 70 may store, for example, data and/or one or more control routines or instructions. The one or more memory devices may be embodied as non-transitory computer readable media, such as Random Access Memory (RAM) devices, NOR or NAND flash memory devices, as well as Read Only Memory (ROM) devices, CD-ROMs, hard disks, floppy disk drives, optical media, solid state storage media, and the like. Controller 70 may receive one or more input signals from one or more input devices 66 and/or sensors 72, and may execute routines or instructions stored in one or more memory devices to generate and deliver one or more command signals to

propulsion devices

28, 30, 32, 34, engine 60, milling drum 50,

transmitters

56, 58, etc.

The sensors 72 may include, for example, one or more of infrared sensors, ultrasonic sensors, cameras, or other types of sensors that may be configured to determine conditions such as roughness, hardness, and/or other characteristics of the floor surface 64. The sensor 72 may be configured to transmit signals to the controller 70 wirelessly or through a wired connection.

Fig. 2 illustrates another exemplary embodiment of a milling machine. In one exemplary embodiment shown in fig. 2, milling machine 20 may be a filling machine, which may also be referred to as a soil stabilizer, a filling machine, a road filling machine, or the like. As with the milling machine 10, the milling machine 20 may include a frame 22,

propulsion devices

28, 30, 32 (not visible in fig. 2), 34 in the form of wheels, and

leg posts

36, 38, 40, 42. In some exemplary embodiments, one or more of the leg posts 36, 38, 40, 42 may be height adjustable such that the height of the frame 22 relative to one or more of the

wheels

28, 30, 32, 34 may be increased or decreased by adjusting the length of one or more of the leg posts 36, 38, 40, 42, respectively. As shown in fig. 2, a leg post 36 may connect the frame 22 to the left front wheel 28, a leg post 38 may connect the frame 22 to the right front wheel 30, a leg post 40 may connect the frame 22 to the left rear wheel 32 (not visible in fig. 2), and a leg post 42 may connect the frame 22 to the right rear wheel 34. Although milling machine 20 has been illustrated in fig. 2 as including

wheels

28, 30, 32, 34, it is contemplated that milling machine 20 may instead include tracks 28, 30, 32, 34. One or more of

wheels

28, 30, 32, 34 may be steerable, allowing milling machine 20 to turn right or left during forward or backward movement on ground surface 64.

Milling drum 50 of milling machine 20 may be located between first end 24 and second end 26. In one exemplary embodiment as shown in fig. 2, milling drum 50 of milling machine 20 may not be directly attached to frame 22. Rather, as shown in fig. 2, milling drum 50 of milling machine 20 may be attached to frame 22 via arm 74. The arms 74 may include a pair of arms (only one of which is visible in fig. 2) disposed on either side of the milling machine 20. The arm 74 may be pivotably attached to the frame 22 and may be configured to rotate relative to the frame 22. One or more actuators may be connected between the frame 22 and the arm 74, and may be configured to move the arm 74 relative to the frame 22. Thus, unlike milling machine 10, milling drum 50 of milling machine 20 may be movable relative to frame 22. However, it is contemplated that, in other exemplary embodiments, milling drum 50 may be directly attached to frame 22 of machine 20 in a manner similar to that described above for machine 10.

Milling drum 50 of milling machine 20 may include cutting tools 52 (or teeth 52). The height of milling drum 50 above the ground surface may be adjusted by rotating arm 74 relative to frame 22 and/or by adjusting one or more of leg posts 36, 38, 40, 42. As milling drum 50 rotates, teeth 52 may contact and tear or cut the ground or road surface. Milling drum 50 may be enclosed within a drum 54, which may help to contain material removed from the ground or road surface by teeth 52. Rotation of milling drum 50 may cause the removed material to be diverted from adjacent front end 76 of drum 54 toward rear end 78 of drum 54. Stabilizing components such as ash, lime, cement, water, etc. may be mixed with the removed material, and a reconstituted mixture of milled material and stabilizing components may be deposited on the ground surface 64 near the rear end 78 of the drum 54.

Similar to the milling machine 10, the milling machine 20 may also include an engine 60, an operator platform 62, one or more control or input devices 66, a controller 70, and one or more sensors 72, all of which may have characteristics similar to those discussed above with respect to the milling machine 10. Additionally, it should be understood that the terms front and rear, as used in this disclosure, are relative terms that may be determined based on the direction of travel of the

milling machine

10 or 20. Also, it should be understood that, as used in this disclosure, left and right are relative terms that may be determined based on a direction of travel facing the milling

machine

10 or 20.

Fig. 3 is a partial cross-sectional view of an

exemplary leg post

36, 38, 40, 42 for milling

machine

10 or 20. The leg strut 36 may include a first (or upper) section 80 and a second (or lower) section 82. The actuator 88 may be disposed within or outside the leg post 36. The first section 80 may be attached to the frame 22. In one exemplary embodiment, the first section 80 may be rigidly attached to the frame 22. First section 80 may extend from frame 22 toward track 28. In some exemplary embodiments, first section 80 may also extend into frame 22 in a direction away from track 28. The second section 82 may be attached to the track 28 and may extend from the track 28 toward the frame 22. In one exemplary embodiment as shown in fig. 3, the first section 80 and the second section 82 may be hollow cylindrical tubes. However, it is contemplated that the first and second sections 80, 82 may have other non-cylindrical shapes. The first and second sections 80, 82 may be configured to slidably move relative to each other. In one exemplary embodiment as shown in fig. 3, the second section 82 may have a smaller cross-section relative to the first section 80 and may be received within the first section 80. However, it is contemplated that in other exemplary embodiments, the first section 80 may have a smaller cross-section relative to the second section 82 and may be received within the second section 82. The first and second sections 80, 82 may form a variable height enclosure within which the actuator 88 may be located. However, it is also contemplated that the actuator 88 may be located outside of the enclosure formed by the first and second sections 80, 82.

Actuators 88 may connect frame 22 with tracks 28. The actuator 88 may include a cylinder 90, a piston 92, and a rod 94. The cylinders 90 may extend from a frame end 100 connected to the frame 22 to a track end 102, which may be disposed between the frame 22 and the track 28. The piston 92 may be slidably disposed within the cylinder 90 and may divide the cylinder 90 into a front end chamber 96 and a rod end chamber 98. That is, the piston 92 may be configured to slide within the cylinder 90 from an adjacent frame end 100 to an adjacent track end 102. The front end chamber 96 may be disposed closer to a frame end 100 of the cylinder 90 and the rod end chamber 98 may be disposed closer to a track end 102 of the cylinder 90. A rod 94 may be connected at one end to the piston 92. The rod 94 may extend from the piston 92 through a track end 102 of the cylinder 90 and may be directly or indirectly connected to the track 28 at an opposite end of the rod 94. In one exemplary embodiment as shown in fig. 3, the rod 94 may be connected to a yoke 132, which in turn may be connected to the track 28. In some exemplary embodiments, the yoke 132 may be fixedly attached to the second section 82 of the leg post 36. In other exemplary embodiments, yoke 132 may be part of track 28 and may be movably attached to second section 82. It is also contemplated that in some embodiments, the yoke 132 may not be attached to the second section 82.

The actuator 88 may be a single acting or double acting hydraulic actuator. For example, one or both of the front end chamber 96 and the rod end chamber 98 of the actuator 88 may be configured to receive and retainA hydraulic fluid. One or both of the front end chamber 96 and the rod end chamber 98 may be connected to a reservoir 140 (see fig. 4A, 4B) configured to store hydraulic fluid. Filling the front end chamber 96 with hydraulic fluid and/or emptying the rod end chamber 98 of hydraulic fluid may slidably move the piston 92 within the cylinder 90 in a direction indicated by arrow "a" from the frame end 100 toward the track end 102. Movement of the piston in direction A may cause the length of the actuator 88 to increase, thereby slidably moving the first and second sections 80, 82 relative to each other, thereby increasing the height "h" of the leg post 36₁". Height h₁And may also correspond to the height of the frame 22 relative to the tracks 28. Height h₁May correspond to the height "h" of the frame 22 relative to the ground surface 64₂"is increased. Similarly, emptying hydraulic fluid from the front end chamber 96 and/or filling the rod end chamber 98 with hydraulic fluid may slidably move the piston 92 within the cylinder 90 in a direction indicated by arrow "B" from the track end 102 toward the frame end 100. Movement of the piston in direction B may reduce the length of the actuator 88, thereby reducing the height "h" of the leg post 36₁", which in turn may reduce the height" h "of the frame 22 relative to the ground surface 64₂". Despite the height h₁Has been shown with respect to the upper surface 136 of the track 28 in FIG. 3, but it is contemplated that in some exemplary embodiments, the height h is₁May instead be measured relative to the upper edge 134 of the track 28. Further, although the above description refers to the leg posts 36 and tracks 28, each of the leg posts 38, 40, 42 connected between the frame 22 and the

tracks

30, 32, 34, respectively, may have structural and functional characteristics similar to those described above with respect to the leg posts 36 and tracks 28.

Fig. 4A shows a schematic view of an exemplary hydraulic damping system 104 for milling

machine

10 or 20. As shown in fig. 4A, the hydraulic damping system 104 may be applied to the

milling machine

10 or 20, which may include two front tracks (e.g., the left front track 28 and the right front track 30) and one rear track 32. The left front track 28 may be connected to the frame 22 via a leg post 36 (see fig. 1), the right front track may be connected to the frame 22 via a leg post 38 (see fig. 1), and the rear track 32 may be connected to the frame 22 via a leg post 40 (see fig. 1). As shown in fig. 4A, the rear tracks 32 may be positioned adjacent the second end 26 of the frame 22 and generally centered along the width "W" of the frame 22.

Left front track 28 may be connected to frame 22 via left front actuator 88, right front track 30 may be connected to frame 22 via right front actuator 108, and rear track 32 may be connected to frame 22 via rear actuator 110.

Actuators

88, 108 and 110 may be located inside or outside leg posts 36, 38 and 40, respectively. The front left actuator 88 may be a single-acting or double-acting hydraulic actuator, and may have structural and functional characteristics similar to those described above with respect to fig. 3. The front right actuator 108 may be a single or double acting hydraulic actuator and may include a cylinder 112, a piston 114, and a rod 116. Piston 114 may be slidably disposed within cylinder 112 and may divide cylinder 112 into a front end chamber 118 and a rod end chamber 120. That is, piston 114 may be configured to slide within cylinder 112. One or both of the front end chamber 118 and the rod end chamber 120 may be configured to hold and receive hydraulic fluid. The cylinder 112 may be connected to the frame 22 adjacent the front end chamber 118. A rod 116 may be connected to the piston 114 at one end and to the track 30 at an opposite end. Similarly, rear actuator 110 may be a single-acting or double-acting hydraulic actuator, and may include a cylinder 122, a piston 124, and a rod 126. The piston 124 may be slidably disposed within the cylinder 122 and may divide the cylinder 122 into a front end chamber 128 and a rod end chamber 130. That is, the piston 124 may be configured to slide within the cylinder 122. One or both of the front end chamber 128 and the rod end chamber 130 may be configured to hold and receive hydraulic fluid. The cylinder 122 may be connected to the frame 22 adjacent the front end chamber 128. The rod 126 may be connected to the piston 124 at one end and to the track 32 at an opposite end.

The milling

machine

10 or 20 may also include a storage tank 140, which may be configured to store hydraulic fluid. One or more of the

front end chambers

96, 118, 128 and/or the

rod end chambers

98, 120, 130 may be connected to a reservoir 140, and may receive hydraulic fluid from or direct hydraulic fluid to the reservoir 140. For example, as shown in fig. 4A, a reservoir fluid conduit 142 may connect the reservoir 140 with the rod end chamber 98 of the actuator 88, a reservoir fluid conduit 144 may connect the reservoir 140 with the rod end chamber 120 of the actuator 108, and a reservoir fluid conduit 146 may connect the reservoir 140 to the rod end chamber 130 of the actuator 110. Thus, for example, hydraulic fluid may flow from the reservoir 140 to one or more of the

rod end chambers

98, 120, 130, or vice versa. Milling

machine

10 or 20 may include additional fluid conduits, control valves, pressure relief valves, pumps, filters, and other hydraulic components that connect

actuators

88, 108, and/or 110 to storage tank 140. Discussion of such components in this disclosure has been omitted for the sake of brevity and clarity.

The hydraulic damping system 104 may include

damper assemblies

150, 160, and 170. For example, the left damper assembly 150 may be associated with the left front actuator 88, the right damper assembly 160 may be associated with the right front actuator 108, and the rear damper assembly 170 may be associated with the rear actuator 110. The left damper assembly 150 may include a left accumulator 152, a left control valve 154, and a left fluid conduit 156. The left accumulator 152 may be connected to the left front actuator 88 via a left fluid conduit 156. For example, the left accumulator 152 may be connected to the front end chamber 96 of the left front actuator 88 via a left fluid conduit 156. A left control valve 154 may be disposed in a fluid conduit 156 between the actuator 88 and the accumulator 152 and may be configured to control hydraulic fluid flow between the front end chamber 96 and the accumulator 152. The right damper assembly 160 may include a right accumulator 162, a right control valve 164, and a right fluid conduit 166. The right accumulator 162 may be connected to the right front actuator 108 via a right fluid conduit 166. For example, the right accumulator 162 may be connected to the front end chamber 118 of the right front actuator 108 via a right fluid conduit 166. A right control valve 164 may be disposed in a right fluid conduit 166 between the actuator 108 and the accumulator 162 and may be configured to control the amount of flowing hydraulic fluid between the front end chamber 118 and the accumulator 162. Similarly, the rear damper assembly 170 may include a rear accumulator 172, a rear control valve 174, and a rear fluid conduit 176. The rear accumulator 172 may be connected to the front end chamber 128 of the rear actuator 110 via a rear fluid conduit 176. A rear control valve 174 may be disposed in a rear fluid conduit 176 between the actuator 110 and the accumulator 172 and may be configured to control hydraulic fluid flow between the front end chamber 128 and the accumulator 172. Although fig. 4A shows three

damper assemblies

150, 160, 170 connected to actuators 88, 108, 110, respectively, it is contemplated that, in various exemplary embodiments, hydraulic damping system 104 may include only some (e.g., any one or two) or all of

damper assemblies

150, 160, 170. As described above, each of the

accumulators

152, 162, 172 may be individually connected to the

actuators

88, 108, 110, respectively. That is, each

accumulator

152, 162, or 172 may not be connected to more than one

actuator

88, 108, or 110.

The

control valves

154, 164, 174 may be multi-position or proportional type valves having valve elements movable to regulate hydraulic fluid flow through the

fluid conduits

156, 166, 176, respectively. The valve elements in the

control valves

154, 164, 174 may be solenoid operable to move between flow passing and flow blocking positions. In the flow passing position, the

control valves

154, 164, 174 may allow hydraulic fluid to flow through the

fluid conduits

156, 166, 176, respectively, substantially without being restricted by the

control valves

154, 164, 174, respectively. In contrast, in the flow blocking position, the

control valves

154, 164, 174 may completely block the flow of hydraulic fluid through the

fluid conduits

156, 166, 176. The valve element of the

control valves

154, 164, 174 may also be selectively moved to various positions between the flow passing and flow blocking positions to achieve variable flow rates of hydraulic fluid in the

fluid conduits

156, 166, 176, respectively.

Fig. 5A illustrates an exemplary accumulator 180. Accumulator 180 may include an enclosure 182 having a fluid inlet 184 and a gas inlet 186. Accumulator 180 may also include a bladder 188 disposed within enclosure 182 and configured to divide enclosure 182 into a gas enclosure 190 and a fluid enclosure 192. In one exemplary embodiment, balloon 188 may be an expandable balloon. Bladder 188 may be configured to enclose a gaseous medium (e.g., a gas such as nitrogen or other inert gas). The accumulator 180 may include a gas conduit 194, which may be configured to allow gas to flow into or out of the gas enclosure 190. A control valve 196 may be disposed in the gas conduit 194. The control valve 196 may have similar structural and functional characteristics as the

control valves

154, 164, 174. Also, similar to control

valves

154, 164, 174, control valve 196 may allow or block gas flow into or out of gas enclosure 190 through gas conduit 194.

The rate at which hydraulic fluid may flow into or out of the fluid enclosure 192 may depend on the pressure of the gaseous medium enclosed in the gas enclosure 190. For example, as hydraulic fluid flows into fluid enclosure 192, bladder 188 may deform, reducing the volume of gas enclosure 190, thereby compressing the enclosed gaseous medium in bladder 188. The increased pressure of the gaseous medium in bladder 188 may act on bladder 188, thereby reducing the rate at which bladder 188 may deform, which in turn may help reduce the flow rate of hydraulic fluid entering fluid enclosure 192.

The pressure of the gaseous medium enclosed in the gas enclosure 190 may also be increased or decreased by allowing the gaseous medium to flow into or out of the gas enclosure 190 via gas conduit 194. In some exemplary embodiments, the controller 70 may be configured to adjust the control valve 196 to control the rate at which gaseous medium may flow into or out of the gas enclosure 190. In some exemplary embodiments, the accumulator 180 may include a pressure sensor 198, which may be configured to measure the pressure of the gaseous medium in the gas enclosure 190. Controller 70 may be configured to selectively adjust a valve element of control valve 196 between a flow blocking position and a flow passing position based on a signal received from pressure sensor 198. For example, the controller 70 may be configured to adjust the valve elements of the control valve 196 to regulate the flow of gaseous medium into or out of the gas capsule 190 to equalize the pressure of the gas capsule 190 with the hydraulic pressure in the front or rod end chamber of the one or

more actuators

88, 108, 110, and/or 248 to which the

accumulator

180 or 200 may be connected. It is also contemplated that controller 70 may be configured to selectively adjust valve elements of control valve 196 based on signals received from one or more input devices 66 and/or signals received from other sensors or components of milling

machine

10 or 20. In other exemplary embodiments, the accumulator 180 may include gaseous media at a predetermined pressure, and the control valve 196 may not be adjusted during operation of the milling machine to maintain the predetermined pressure in the accumulator 180.

Fig. 5B illustrates another exemplary embodiment of accumulator 200. The accumulator 200 may include an enclosure 202 that may have an end wall 204. The accumulator 200 may include a piston 206, which may be slidably disposed within the enclosure 202, and may be configured to divide the enclosure 202 into a gas enclosure 208 and a fluid enclosure 210. The gas enclosure 208 may be configured to enclose a gaseous medium, while the fluid enclosure 210 may be configured to enclose a hydraulic fluid. The accumulator 200 may include a fluid inlet 212 that may allow hydraulic fluid to enter or exit the fluid enclosure 210 and a gas inlet 214 that may allow gaseous media to enter or exit the gas enclosure 208. The accumulator 200 may include a gas conduit 216, which may be configured to allow a gaseous medium to flow into or out of the gas enclosure 208. A control valve 218 may be disposed in the gas conduit 216. The control valve 218 may have similar structural and functional characteristics as the

control valves

154, 164, 174. Also, similar to control

valves

154, 164, 174, control valve 218 may also allow or block the flow of gas through gas conduit 216.

The rate at which hydraulic fluid may flow into the fluid enclosure 210 may depend on the pressure of the gas in the gas enclosure 208. For example, as hydraulic fluid flows into the fluid enclosure 210, the piston 206 may move in a direction toward the gas inlet 214, reducing the volume of the gas enclosure 208 and compressing the gaseous medium in the gas enclosure 208. The increased pressure of the gaseous medium enclosed in the gas enclosure 208 may exert an opposing force on the piston 206, thereby reducing the rate at which the piston 206 may move toward the gas inlet 214. This in turn may reduce the rate at which hydraulic fluid may flow into the fluid enclosure 210.

The pressure of the gaseous medium enclosed in the gas enclosure 208 may also be increased or decreased by allowing the gaseous medium to flow into or out of the gas enclosure 208 via the gas conduit 216. In some exemplary embodiments, the controller 70 may be configured to adjust the control valve 218 to control the rate at which gaseous medium may flow into or out of the gas enclosure 208. In some exemplary embodiments, the accumulator 200 may include a pressure sensor 220, which may be configured to measure the pressure of the gaseous medium in the gas enclosure 208. The controller 70 may be configured to selectively adjust the valve element of the control valve 218 between the flow blocking position and the flow passing position based on a signal received from the pressure sensor 220. For example, the controller 70 may be configured to adjust the valve element of the control valve 218 to regulate the flow of gaseous medium into or out of the gas enclosure 208 to equalize the pressure of the gas enclosure 208 with the hydraulic pressure in the front or rod end chamber of the one or

more actuators

88, 108, 110, and/or 248 to which the

accumulator

180 or 200 may be connected. It is also contemplated that controller 70 may be configured to selectively adjust the valve elements of control valve 218 based on signals received from one or more input devices 66 and/or signals received from other sensors or components of milling

machine

10 or 20. In other exemplary embodiments, the accumulator 200 may include gaseous media at a predetermined pressure, and the control valve 218 may not be adjusted during operation of the milling machine to maintain the predetermined pressure in the accumulator 200.

Although the accumulator 200 has been described as including a piston 206, in some exemplary embodiments, the piston 206 may be replaced by a diaphragm attached to an inner wall of the enclosure 202. The diaphragm may separate the gas enclosure 208 from the fluid enclosure 210. The diaphragm may be configured to deform and change shape based on the pressure of the gaseous medium in the gas enclosure 208 and/or the pressure of the hydraulic fluid in the fluid enclosure 210. The pressure of the gaseous medium in gas enclosure 208 may determine the rate at which the diaphragm may deform when acted upon by hydraulic fluid flowing into or out of fluid enclosure 210. The rate of deformation of the diaphragm, in turn, may determine the rate at which hydraulic fluid may flow into or out of the fluid enclosure 210.

Returning to fig. 4A, the

accumulators

152, 162, 172 may take the form of any of the

accumulators

180 or 200 discussed above with respect to fig. 5A and 5B. The

accumulators

152, 162, 172 may be configured to attenuate the rate at which the height of the frame 22 may change relative to the ground surface 64. For example, when the left front track 28 passes over an obstacle (such as a bump on the ground surface 64), the left front track 28 and the piston 92 may be forced to move in a direction from the ground surface 64 toward the frame 22. This movement of the piston 92 may reduce the volume of the front end chamber 96, forcing hydraulic fluid to flow from the front end chamber 96 to the accumulator 152 via the fluid conduit 156.

The pressure of the gaseous medium in the accumulator 152 may determine the rate at which hydraulic fluid may flow from the front end chamber 96 to the accumulator 152. For example, as explained above with respect to

accumulators

180 and 200, as hydraulic fluid flows into accumulator 152, the gaseous medium in the gas enclosure of accumulator 152 may be compressed. The increased pressure of the gaseous medium in the gas enclosure of the accumulator 152 may reduce the rate at which hydraulic fluid may flow into the accumulator 152. Additionally or alternatively, the controller 70 may be configured to adjust the control valve 154 to control (e.g., decrease or increase) the rate at which hydraulic fluid may flow from the front end chamber 96 to the accumulator 152. Controlling the rate at which hydraulic fluid may flow from the front end chamber 96 to the accumulator 152 may also help control the rate at which the piston 92 and the left front track 28 may move toward the frame 22. This, in turn, may help to reduce the rate at which the frame 22 may move toward or away from the ground surface 64, which, in turn, may improve the comfort of an operator located in the operator platform 62.

Similarly, when the left front track 28 encounters a depression in the ground surface 64, the piston 92 may be forced toward the ground surface 64 and away from the frame 22. This movement of the piston 92 may cause the volume of the front end chamber 96 to increase, thereby causing hydraulic fluid from the accumulator 152 to flow into the front end chamber 96 via the fluid conduit 156. The pressure of the gaseous medium in the accumulator 152 and/or the amount of opening of the control valve 154 may help regulate (e.g., increase or decrease) the flow rate of hydraulic fluid from the accumulator 152 to the front end chamber 96, which may control the rate at which the piston 92 may move away from the frame 22. This, in turn, may help to reduce the rate at which the frame 22 may move toward or away from the ground surface 64, improving the comfort of an operator located in the operator platform 62. While the above description of the hydraulic damping system 104 has been provided in terms of the components of the left front track 28 and the damper assembly 150, it should be understood that the movement of the

pistons

114 and 124 corresponding to the right front track 30 and the rear track 32 will be similarly accommodated by the

damper assemblies

160 and 170, respectively.

As further shown in fig. 4A, the milling

machine

10 or 20 may include a drum speed sensor 222 and

ground speed sensors

224, 226, 228. Drum speed sensor 222 may be associated with milling drum 50 and may be configured to measure a rotational speed (e.g., rpm or revolutions per minute) of milling drum 50. Drum speed sensor 222 may be configured to generate and send one or more signals indicative of the rotational speed of milling drum 50 to controller 70. It is also contemplated that controller 70 may additionally or alternatively determine the rotational speed of the milling drum based on other parameters, such as the rotational speed of the engine, the gear ratio or gear ratio, etc.

Ground speed sensors

224, 226, 228 may be associated with the left front track 28, the right front track 30, and the rear track 32, respectively, and may be configured to measure the speed (e.g., feet per second, miles per hour, etc.) at which the

tracks

28, 30, 34 may propel over the ground surface 64. The

ground speed sensors

224, 226, 228 may be configured to generate one or more signals indicative of the ground speed of the left front track 28, the right front track 30, and the rear track 32, respectively, and may send the one or more signals to the controller 70. However, it is contemplated that controller 70 may additionally or alternatively determine the ground speed of milling

machine

10 or 20 in other manners, such as, for example, using GPS sensors, inertial sensors, flow rates or pressures of hydraulic fluid in hydraulic motors associated with

tracks

28, 30, 32, etc.

In some exemplary embodiments, the

control valves

154, 164, 174 may initially be fully closed such that the hydraulic damping system 104 may be deactivated. The hydraulic damping system 104 may be activated by opening one or more of the

control valves

154, 164, 174 from a fully closed position. One or

more control valves

154, 164, 174 may be opened by controller 70 from their respective fully closed positions based on signals received from one or more of input device 66, drum speed sensor 222,

ground speed sensors

224, 226, 228, and/or any other sensors associated with milling

machine

10 or 20. For example, an operator may engage one or more input devices 66 for activating the hydraulic damping system 104. In response to signals received from input device 66, controller 70 may selectively open one or

more control valves

154, 164, 174, allowing one or

more accumulators

152, 162, 172, respectively, to regulate the flow of hydraulic fluid into or out of

front end chambers

96, 118, 128, respectively.

Additionally or alternatively, in some example embodiments, controller 70 may selectively open one or

more control valves

154, 164, 174 based on the rotational speed of milling drum 50. For example, controller 70 may selectively open one or more of

control valves

154, 164, 174 when the rotational speed of milling drum 50, as determined by drum speed sensor 222, for example, exceeds a threshold drum speed. In other exemplary embodiments, the controller 70 may selectively open one or more of the

control valves

154, 164, 174 based on, for example, a ground speed determined by one or more of the

ground speed sensors

224, 226, 228. For example, the controller 70 may selectively open one or more of the

control valves

154, 164, 174 when the ground speed exceeds a threshold ground speed of the

milling machine

10 or 20.

Fig. 4B illustrates a schematic view of another exemplary hydraulic damping system 240 for milling

machine

10 or 20. As shown in fig. 4B, the hydraulic damping system 240 may be applied to a

milling machine

10 or 20 that includes two front tracks (e.g., left front track 28 and right front track 30) and two rear tracks (e.g., left rear track 32 and right rear track 34). As described above with respect to fig. 4A, the left front track 28 may be connected to the frame 22 via a leg post 36 (see fig. 1), the right front track may be connected to the frame 22 via a leg post 38 (see fig. 1), and the left rear track 32 may be connected to the frame 22 via a leg post 40 (see fig. 1). Further, the right rear track 34 may be connected to the frame 22 via a leg post 42 (see fig. 1). However, as shown in fig. 4B, the left rear track 32 may be positioned adjacent one side of the frame 22, and the right rear track 34 may be positioned adjacent an opposite side of the frame 22 and laterally spaced from the left rear track 32 along the width W of the frame 22.

Left front track 28 may be connected to frame 22 via a left front actuator 88, right front track 30 may be connected to frame 22 via a right front actuator 108, left rear track 32 may be connected to frame 22 via a left rear actuator 110, and right rear track 34 may be connected to frame 22 via a right rear actuator 248. The

actuators

88, 108, 110, and 248 may be located inside or outside of the leg posts 36, 38, 40, 42, respectively. The front left actuator 88, front right actuator 108, and rear left actuator 110 may have similar structural and functional characteristics as described above. Right rear actuator 248 may include a cylinder 250, a piston 252, and a rod 254. The piston 252 may be slidably disposed within the cylinder 250 and may divide the cylinder 250 into a front end chamber 256 and a rod end chamber 258. That is, the piston 252 may be configured to slide within the cylinder 250. One or both of front end chamber 256 and rod end chamber 258 may be configured to hold and receive hydraulic fluid. The cylinder 250 may be connected to the frame 22 adjacent the front end chamber 256. The rod 254 may be connected to the piston 252 at one end and to the track 34 at an opposite end.

As also shown in fig. 4B, the left rear actuator 110 and the right rear actuator 248 may be connected to each other to form a fully floating shaft. For example, the front end chamber 128 of the left rear actuator 110 may be connected to the front end chamber 256 of the right rear actuator 248 via a front end fluid conduit 260. Similarly, the rod end chamber 130 of the left rear actuator 110 may be connected to the rod end chamber 258 of the right rear actuator 248 via a rod end fluid conduit 262.

Hydraulic damping system 240 may include

damper assemblies

150, 160, and 170, which may have similar structural and functional characteristics as described above with respect to hydraulic damping system 104. The left damper assembly 150 may be associated with the actuator 88 and the right damper assembly 160 may be associated with the actuator 108. The left and

right damper assemblies

150 and 160 may be separately connected to the left and right

front actuators

88 and 108, respectively, similar to that discussed above with respect to the hydraulic damping system 104 of fig. 4A. That is, each of the left and

right damper assemblies

150 and 160 may be connected to only one

actuator

88 and 108, respectively. However, the damper assembly 170 may be connected to both the

rear actuators

110 and 248. Similar to the hydraulic damping system 104, the damper assembly 170 of the hydraulic damping system 240 may include an accumulator 172, a control valve 174, and a fluid conduit 176. The accumulator 172 may be connected to a front end fluid conduit 260 via a rear fluid conduit 176, and thus to the

front end chambers

128 and 256 of both the left rear actuator 110 and the right rear actuator 248, respectively. The control valve 174 may be disposed in the fluid conduit 176 between the front end fluid conduit 260 and the accumulator 172, and may be configured to control hydraulic fluid flow between the

front end chambers

128, 256 and the accumulator 172.

Although fig. 4B shows three

damper assemblies

150, 160, 170 connected to actuators 88, 108 and a front end fluid conduit 260, it is contemplated that in various exemplary embodiments, hydraulic damping system 240 may include only some (e.g., any one or two) or all of

damper assemblies

150, 160, 170. It is also contemplated that, in some exemplary embodiments, hydraulic damping system 240 may include more than three

damper assemblies

150, 160, 170. For example, in some exemplary embodiments, the

front end chambers

128, 256 may not be connected to each other and the

rod end chambers

130, 258 may not be connected to each other, but instead a separate damper assembly may be separately connected to each of the left and right

rear actuators

110, 248.

As also shown in fig. 4B, the milling

machine

10 or 20 may include a drum speed sensor 222 and

ground speed sensors

224, 226, 228, 266. The drum speed sensor 222 and

ground speed sensors

224, 226, 228 shown in fig. 4B may have similar structural and functional characteristics to those of the corresponding sensors discussed above with respect to fig. 4A. Further, a ground speed sensor 266 may be associated with the right rear track 34 and may be configured to determine a ground speed of the right rear track 34 relative to the ground surface 64. The ground speed sensor 266 may have similar structural and functional characteristics as those of the

ground speed sensors

224, 226, 228 discussed above. The controller 70 may activate the hydraulic damping system 240 based on signals received from one or more input devices 66, the drum speed sensor 222, or one or more

ground speed sensors

224, 226, 228, 266 in a manner similar to that described above with reference to the hydraulic damping system 104 of fig. 4A.

As shown in fig. 1 and 2, the milling

machine

10 or 20 may include one or more sensors 72 configured to determine conditions such as roughness, hardness, porosity, and/or other characteristics of the ground surface 64. Controller 70 may be configured to adjust valve elements in one or more of

control valves

154, 164, or 174 such that

accumulators

152, 162, and 172 may provide different levels of hydraulic damping based on, for example, characteristics of ground surface 64 as determined by one or more sensors 72. For example, the controller 70 may be configured to adjust the valve elements in one or more of the

control valves

154, 164, or 174 such that the

accumulators

152, 162, and 172 may provide increased hydraulic damping when the ground surface 64 is relatively hard as compared to when the ground surface is relatively soft. Specifically, the controller 70 may be configured to selectively adjust the valve element such that the

control valve

154, 164, or 174 allows a higher flow rate of hydraulic fluid into or out of the

front end chamber

96, 118, or 128 when the floor surface 64 is relatively hard than when the floor surface is relatively soft. It is also contemplated that controller 70 may be configured to selectively adjust valve elements in control valves 196 or 218 associated with one or more of

accumulators

152, 162, and 172 to control the gas pressure in

accumulators

152, 162, and 172, which in turn may adjust the level of damping provided by

accumulators

152, 162, and/or 172. Valve 196 or 218 may be adjustable prior to beginning a milling operation with milling

machine

10 or 20 and/or during a milling operation performed by milling

machine

10 or 20.

It is also contemplated that, in some exemplary embodiments, controller 70 may be configured to selectively adjust valve elements in

control valves

154, 164, and/or 174 based on an operator requested level of hydraulic damping. The operator may be able to specify the desired level of damping using the input device 66. For example, the input device 66 may be a button, joystick, scroll wheel, slider, touch screen element, or the like, which may have multiple positions corresponding to different damping levels (e.g., low, medium, high). For example, when the controller 70 receives a signal from the input device 66 indicating that a low level of damping (e.g., stiffer legs) is desired, the controller 70 may adjust one or more of the

control valves

154, 164, 174, respectively, to allow a relatively low flow rate of hydraulic fluid into or out of the

front end chambers

96, 118, or 128. In contrast, when, for example, the controller 70 receives a signal from the input device 66 indicating that a high level of damping (e.g., softer legs) is required, the controller 70 may adjust one or more of the

control valves

154, 164, 174 to their flow-passing positions to allow hydraulic fluid to flow into or out of the

front end chambers

96, 118, or 128, respectively, without restriction. For example, when the controller 70 receives a signal from the input device 66 indicating that a medium level of damping is required, the controller 70 may adjust one or more of the

control valves

154, 164, 174 by an amount that may range between the fully blocking and fully passing positions of the

control valves

154, 164, 174. Although only three damping levels are described, it is contemplated that controller 70 may be configured to adjust one or more of

control valves

154, 164, 174 to achieve more than three damping levels.

It is also contemplated that controller 70 may determine the damping level based on the ground speed of milling

machine

10 or 20. For example, the controller 70 may allow for a relatively higher level of damping at higher ground speeds as compared to lower ground speeds. The controller 70 may also determine the level of damping based on other parameters, such as engine speed, engine torque or power, drum speed, drum torque or power, hydraulic pressure in one or more hydraulic motors, and the like.

The method of operating the

milling machine

10 or 20 with hydraulic damping by the hydraulic damping

system

104 or 240 will be described in greater detail below.

INDUSTRIAL APPLICABILITY

The hydraulic damping

systems

104, 240 of the present disclosure may be used on the

milling machine

10 or 20 to reduce the amount of movement of the frame 22 of the

milling machine

10 or 20 relative to the ground surface 64 as one or more of the

tracks

28, 30, 32, 34 travel over irregularities (e.g., bumps or dents) in the ground surface 64. By reducing shifting or tilting of frame 22 relative to ground surface 64, the disclosed hydraulic damping

systems

104, 240 may help improve operator comfort when milling

machine

10 or 20 is transported through a work site or from one work site to another.

Fig. 6 illustrates an example method 600 of operating the

milling machine

10 or 20 with the hydraulic damping

system

104 or 240 as the

milling machine

10 or 20 travels over the ground surface 64. The order and arrangement of the steps of method 600 are provided for illustrative purposes. As will be appreciated from the present disclosure, the method 600 may be modified by, for example, adding, combining, removing, and/or rearranging the steps of the method 600. The method 600 may be performed by the controller 70. Although the method 600 is described below with reference to the front actuator 88 and the damper assembly 150, the method 600 and its steps as described below and as shown in fig. 6 are equally applicable to the front actuator 108, the

rear actuators

110, 248 and the

damper assemblies

160, 170.

Method 600 may include the step of not contacting milling drum 50 with ground surface 64 (step 602). An operator may perform such operations prior to, for example, transporting

milling machine

10 or 20 from one work site to another. The operator may do so at the milling machine10 or 20 are being transported from one location to another to ensure, for example, that milling drum teeth 52 do not damage ground surface 64. Controller 70 may receive a signal from one or more input devices 66 indicating that an operator desires to raise frame 22 of milling

machine

10 or 20 so that teeth 52 of milling drum 50 are spaced away from ground surface 64. Controller 70 may cause one or more pumps to pump hydraulic fluid from reservoir 146 into one or more of

front end chambers

96, 118, 128, and/or 256 to increase height h₁、h₂Thereby raising the frame 22. Additionally or alternatively, on milling machine 20, controller 70 may cause one or more actuators connected to arm 74 to be operated such that arm 74 may be pivoted toward frame 22 to disengage milling drum 50 from ground surface 64.

The method 600 may include the step of determining whether hydraulic damping has been activated (step 604). Operator platform 62 may include an input device 66 (e.g., a button, switch, joystick, touch screen, etc.) that may be configured to activate hydraulic damping in one position and deactivate (or terminate) hydraulic damping in another position. The controller 70 may monitor signals from one or more of the input devices 66 to determine whether hydraulic damping has been activated. In some embodiments, step 604 may be omitted, and controller 70 may determine whether to initiate hydraulic damping based on drum speed, ground speed, or other parameters associated with milling

machine

10 or 20.

When controller 70 determines that hydraulic damping has not been activated (step 604: NO), controller 70 may return to step 604 to monitor one or more input devices 66. However, when the controller 70 determines that hydraulic damping has been activated (step 604: YES), the controller 70 may proceed to step 606. Controller 70 may determine that hydraulic damping has begun, for example, when an operator switches input device 66 to a position associated with the initiation of hydraulic damping.

Method 600 may include the step of determining whether a ground speed of

machine

10 or 20 is greater than a threshold ground speed (step 606). Controller 70 may receive signals from one or more of

ground speed sensors

224, 226, 228, and/or 266. The controller 70 may determine the ground speed of the

milling machine

10 or 20 from measurements (or signals) received from the

ground speed sensors

224, 226, 228, and/or 266. The controller 70 may determine the ground speed based on the maximum or minimum values reported by the

ground speed sensors

224, 226, 228, and/or 266, by averaging the values reported by the

ground speed sensors

224, 226, 228, and/or 266, or by performing known mathematical operations on the values reported by the

ground speed sensors

224, 226, 228, and/or 266. It is also contemplated that controller 70 may determine the ground speed of milling

machine

10 or 20 in other manners, such as by using GPS sensors, inertial sensors, hydraulic fluid flow rates or pressures of hydraulic fluid in one or more hydraulic motors associated with tracks or

wheels

28, 30, 32, 34, or based on parameters such as engine power, milling drum torque, etc.

The controller 70 may determine whether the ground speed of the

milling machine

10 or 20 is greater than a threshold ground speed. The threshold ground speed may be predetermined and preset in controller 70, determined by controller 70 based on one or more algorithms or instructions stored in a memory associated with controller 70, or may be input by an operator of milling

machine

10 or 20 using input device 66. When controller 70 determines that the ground speed does not exceed the threshold ground speed (step 606: no), controller 70 may return to step 604 to monitor one or more input devices 66. However, when the controller 70 determines that the ground speed is greater than the threshold ground speed (step 606: YES), the controller 70 may proceed to step 608. Thus, the controller 70 may help ensure that hydraulic damping is only activated when the

milling machine

10 or 20 is traveling at a sufficiently high ground speed (e.g., above a threshold ground speed). At ground speeds less than the threshold ground speed, hydraulic damping may not need to be activated because irregularities on the ground surface 64 may cause minimal or no operator discomfort at those ground speeds. It is also contemplated that during milling operations, controller 70 may close

valves

154, 164, and 174 to provide a stable frame 22.

The method 600 may include the step of opening one or more of the

control valves

154, 164, 174 (step 608). The controller 70 may activate the hydraulic damping

system

104 or 240 by moving the valve elements of the one or

more control valves

154, 164, 174 from the flow blocking position to allow hydraulic fluid to flow from or into the one or

more accumulators

152, 162, 172 from the one or more

front end chambers

96, 118, 128, and/or 256. Opening one or

more control valves

154, 164, 174 in this manner may allow

accumulators

152, 162, and 172 to adjust the rate at which

pistons

92, 114, 124, and/or 252 move in their

respective cylinders

90, 112, 122, and/or 250, respectively. This, in turn, may help to reduce the rate at which the frame 22 may move toward or away from the ground surface 64, thereby improving operator comfort.

Method 600 may include the step of determining whether the ground speed of milling

machine

10 or 20 has decreased below a threshold ground speed (step 610). Controller 70 may determine the ground speed of milling

machine

10 or 20 in a manner similar to that discussed above with reference to, for example, step 606. When controller 70 determines that the ground speed is greater than or equal to the threshold ground speed (step 606: yes), controller 70 may proceed to step 612 of determining whether hydraulic damping has ended. However, when the controller 70 determines that the ground speed is less than the threshold ground (step 606: YES), the controller 70 may proceed to step 614 which deactivates the hydraulic damping

system

104 or 240.

Method 600 may include the step of determining whether hydraulic damping has ended (step 612). The controller 70 may monitor signals from one or more input devices 66 to determine whether hydraulic damping has ended, for example, by an operator. For example, the operator may switch input device 66 to a position associated with closing hydraulic damping. When the controller 70 determines that hydraulic damping has ended (step 612: yes), the controller 70 may proceed to step 614, which deactivates the hydraulic damping

system

104 or 240. However, when the controller 70 determines that hydraulic damping has not ended (step 612: NO), the controller 70 may return to step 610.

The method 600 may include the step of closing the

control valves

154, 164, and 174 (step 614) to deactivate the hydraulic damping

system

104 or 240. For example, step 614 may be performed by controller 70 when the operator provides an input to end hydraulic damping using one or more input devices 66. Step 614 may also be performed by controller 70 when, for example, the ground speed of milling

machine

10 or 20 is less than the threshold ground speed. Controller 70 may move the valve elements in

control valves

154, 164, and 174 to their respective flow blocking positions, thereby blocking hydraulic fluid flow to or from

accumulators

152, 162, 172, respectively. Blocking the flow of hydraulic fluid in this manner may prevent the

accumulators

152, 162, 172 from regulating the flow rate of hydraulic fluid into or out of the

front end chambers

86, 118, 128, and/or 256, thereby eliminating the hydraulic damping effect provided by the

accumulators

152, 162, 172. After completing step 614, method 600 may return to step 604.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed milling machine and hydraulic damping system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed milling machine and hydraulic damping system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A milling machine, comprising:

a frame;

a first track and a second track connected to a first end of the frame;

a third track connected to a second end of the frame disposed opposite the first end;

a first actuator connecting the frame and the first track;

a second actuator connecting the frame and the second track;

a third actuator connecting the frame and the third track, each of the first, second, and third actuators configured to adjust a height of the frame relative to a respective one of the first, second, and third tracks;

a milling drum attached to the frame between the first end and the second end;

a damper assembly attached to at least one of the first and second actuators, the damper assembly comprising:

an accumulator in fluid communication with at least one of the first and second actuators; and

a control valve configured to control fluid flow between the accumulator and at least one of the first and second actuators.

2. The milling machine of claim 1, wherein each of the first, second, and third actuators includes:

a front end chamber;

a rod end chamber; and

a piston separating the front end chamber and the rod end chamber, at least one of the front end chamber and the rod end chamber comprising hydraulic fluid.

3. The milling machine of claim 2, wherein a fluid conduit connects the accumulator with one of the front end chamber or the rod end chamber of at least one of the first and second actuators.

4. The milling machine of claim 3, further comprising:

a reservoir configured to store the hydraulic fluid; and

a reservoir fluid conduit connecting the other of the front end chamber or the rod end chamber of at least one of the first and second actuators to the reservoir.

5. The milling machine of claim 2, further comprising:

a fourth track connected to a second end of the frame; and

a fourth actuator connecting the frame and the fourth track, the fourth actuator configured to adjust a height of the frame relative to the fourth track.

6. The milling machine of claim 5, wherein

Each of the third actuator and the fourth actuator includes:

a front end chamber;

a rod end chamber; and

a piston separating the front end chamber and the rod end chamber;

the front end chamber of the third actuator is connected to the front end chamber of the fourth actuator, and

the rod end chamber of the third actuator is connected to the rod end chamber of the fourth actuator.

7. The milling machine of claim 1, wherein the accumulator comprises:

a gas enclosure configured to enclose a gaseous medium; and

a fluid enclosure configured to hold hydraulic fluid received from the first actuator or the second actuator, the gas enclosure and the fluid enclosure being separate from one another.

8. The milling machine of claim 7, wherein the fluid conduit connects a fluid enclosure of the accumulator with at least one of the first actuator or the second actuator.

9. The milling machine of claim 7, wherein the gas enclosure and the fluid enclosure are separated by an accumulator piston.

10. The milling machine of claim 7, wherein the gas enclosure and the fluid enclosure are separated by a bulkhead.

11. The milling machine of claim 7, wherein the gas enclosure includes a bladder surrounding the gaseous medium, the bladder separating the gas enclosure and the fluid enclosure.

12. The milling machine of claim 1, further comprising a controller configured to selectively open the control valve.

13. The milling machine of claim 12, wherein the controller is further configured to:

receiving input from an input device associated with the milling machine, an

Selectively opening the control valve based on the received input.

14. The milling machine of claim 12, further comprising:

a speed sensor configured to measure a ground speed of the milling machine, wherein

The controller is configured to selectively open the control valve when the ground speed exceeds a threshold ground speed.

15. A milling machine, comprising:

a frame;

a left front track disposed adjacent a front end of the frame;

a right front track disposed adjacent the front end and spaced apart from the left front track;

at least one rear track disposed adjacent a rear end of the frame;

a left front actuator connecting the frame and the left front track;

a right front actuator connecting the frame and the right front track;

a rear actuator connecting the frame and the at least one rear track,

each of the left front actuator, the right front actuator, and the rear actuator configured to selectively adjust a height of the frame relative to the left front track, the right front track, and the at least one rear track, respectively,

each of the front left actuator, the front right actuator, and the rear actuator includes a front end chamber and a rod end chamber separated by a piston,

a milling drum attached to the frame between a front end and a rear end of the frame;

an engine configured to:

propelling the front left track, the front right track, and the at least one rear track in a forward or rearward direction, an

Rotating the milling drum;

a left damper assembly, the left damper assembly comprising:

a left accumulator;

a left fluid conduit connecting the left accumulator to a front end chamber of the left front actuator; and

a left control valve disposed in the left fluid conduit;

a right damper assembly, the right damper assembly comprising:

a right accumulator;

a right fluid conduit connecting the right accumulator to a front end chamber of the right front actuator; and

a right control valve disposed in the right fluid conduit; and

a controller configured to selectively adjust at least one of the left and right control valves.